The present invention relates generally to barriers and other devices used to repel or direct the movement of migrating fish away from turbine intakes and other danger points at dams, hydroelectric facilities, and water intakes in lakes and rivers. More particularly, the present invention describes a system for directing the movement of fish in which the system uses multiple underwater strobe lights strategically positioned and controlled to direct fish away from and towards desired locations.
Hydroelectric power plants and dams have been used throughout the United States and the world with great effectiveness in electric power generation, irrigation, and flood control schemes. However, the increasing use of obstructions across rivers and other navigable waterways has created problems of its own, including deleterious effects on fish populations. For example, hydroelectric dam turbine intakes are a natural attraction point for schooling and migrating fish. If fish are allowed to enter those intakes, large numbers of fish are killed in relative short periods of time. Such fish kills, in turn, can cause damage to the facilities themselves. Also, dams and other structures placed across rivers can interfere with the natural migratory patterns of fish that have been established over the years. If these fish are not allowed to pass the dam and are obstructed from following their natural migratory waterways, fish populations can be greatly impaired. Similar problems can occur at municipal and industrial water intake sites, where large numbers of fish can be drawn into the intake. Therefore, it is important that some means be provided to direct migrating fish around or through a dam, obstruction, or intake so that they can reach their natural spawning grounds.
In response to these issues, federal and state agencies have become increasingly active in establishing a regulatory scheme for the protection of fish in these environments. Accordingly, a variety of physical barrier technologies have been developed in the prior art. These prior art technologies include the use of barrier nets, fish lifts, racks, mesh screens, and louvered bypasses. Unfortunately, such physical barriers have not been optimally efficient in protecting or diverting fish. Moreover, the installation of physical barriers can be extremely expensive, in that custom barrier designs must be developed for each location. Ongoing maintenance costs are also a significant negative factor in the use of physical barriers to control fish.
As an alternative to the use of physical fish barriers, experiments have been conducted in the prior art in the use of strobe lighting as a means to repel fish or otherwise control or direct their movement as they confront or approach a dam or other water intake. These experimental studies have demonstrated that strobe lights produce strong avoidance behavior in a variety of fish species on a consistent basis. In addition, the fish who show this avoidance behavior do not show a tendency to become acclimated to strobe light stimuli, even after prolonged exposure.
The strobe light systems used in the prior art experiments for the control of fish behavior have been deficient in a number of respects, particularly in regards to the development of a commercially useful system which can be easily adapted, installed, and used in a wide variety of physical and aquatic environments and that can be used, without significant modification, to control the behavior of one or more of multiple fish varieties. Thus, for example, variations in ambient water turbidity, water flow rate, flow direction, and water temperature, can directly impact the efficiency of fish control using strobe light systems. In addition, experimentation relating to the development of the present invention has shown that adjustment of flash intensity, flash frequency, and flash sequence is necessary in order to optimally adapt a strobe light fish control system to a particular environment and to a particular species of fish. Prior art systems have not allowed this degree of flexibility and control leading, to the conclusion that such systems can only be considered to be experimental rather than commercially useful.
For behavioral control of fish during a short migration season, there is only a very narrow window of opportunity to adapt a strobe light control system to that species of fish and to the particular environmental conditions encountered. Therefore, real time reaction and control of the system to varying ambient conditions and fish behavior is an important factor. Such control is not found in any of the prior art experimental systems. Furthermore, a short migration season also requires that a system be mobile to be positioned quickly and efficiently by a dam or other intake so as to provide a deterrence for the fish and then be able to move on to another site.
Another problem found with prior art strobe light fish control systems relate to the longevity of the crucial underwater portion of the system, that being the multiple strobe light flash heads. Much of the prior experimentation with such systems has been used in conjunction with flash heads mounted at or near the water surface, attached to floating structures. However, a universally adaptable, commercially useable fish control system using multiple strobe flash heads must be capable of installation at significant depths below the water line, up to perhaps one hundred-fifty feet. This produces a set of problems of its own, particularly in heat management. The preferred means of generating illumination from a strobe flash head is the xenon tube which is both durable and highly efficient. However, the heat generated by the xenon tube and related components must be carefully controlled, particularly in an underwater location, so that the flash head will not fail prematurely because of excessive heat buildup. Experimental prior art strobe light fish control systems have relied on relatively crude adaptations of strobe light devices which have not fully met the needs for deep water submersion, durability, and high flash intensity.
What is needed, then, is a system for the control of fish movement using strobe lights which can be easily installed and adapted to a wide variety of physical environments, can be controlled and adjusted to influence the behavior of a wide variety of fish species, and which carefully deals with flash head heat management in order to prolong the durability of the system.